Agricultural combines are known in the art to harvest a variety of different types of grains. As used herein, the term "grain" is meant to include corn, wheat, rye, oats, barley, flax seed, sorghum, soy beans, mixed grain, and any other food grains, feed grains, and oil seeds.
Under normal operating conditions, the combine will reap the grain stalks through a crop harvesting apparatus that is designed for the particular crop being harvested. An infeed apparatus is connected between the frame of the combine and the crop harvesting apparatus to transfer the crop into a separating apparatus. The separating apparatus threshes the harvested crop materials to separate grain from the material other than grain.
While the separating apparatus acts to separate a substantial portion of the crop or grain from the material other than grain, some chaff and/or straw remains intermixed with the grain and a further cleaning or separating action is normally required. This further separation is normally achieved in a cleaning section of the combine.
The cleaning section of a combine is generally located beneath the separating apparatus. The cleaning section of a typical agricultural combine includes two or more reciprocally mounted sieves with a fan that blows air upwardly through the sieves. The reciprocation of the sieves facilitates arrangement of the grain and other materials in a crop layer, or mat, on top of the sieves.
Each sieve of the cleaning section preferably includes a series of adjacent slats or louvers. A series of transversely elongated openings or passages are defined between the confronting upper and lower surfaces of adjacent slats. The elongated openings or passages separate the material such that grain is allowed to fall through the openings but causing larger pieces of material other than grain to be moved rearward and off the sieves.
Separation of the crop material is facilitated by the air from the fan flowing upwardly through the sieves. The upwardly directed air creates a force which urges residue material, including straw, chaff and the like, to float on top of the sieve and into an airborne state such that it may be directed toward and expelled from a discharge end of the combine. On the other hand, the clean grain tends to move to the sieve and fall through the openings or passages between adjacent slats into a clean grain collector as they are heavier than the other materials.
To enhance versatility of the combine such that it can be used to harvest more than one type of grain, the slats on the cleaning sieves are angularly adjustable relative to one another. The angular adjustability of the slats allows the size of the openings or passages between adjacent slats to be changed to control the size of the material that is allowed to fall through the passages or openings, as well as to regulate the upward flow of air through the sieves thereby achieving the desired degree of material separation.
To further enhance the efficiency of the combine, each cleaning sieve is typically divided into sections. Each sieve section comprises a series of slats or louvers which are similarly disposed relative to each other for separating the material deposited onto that particular section of the sieve. Configuring the sieve with various sections allows the openings or passages between the various sections to be sized. Further, the various sections of the cleaning sieve can be adjusted relative to one another in such a way that the openings between adjacent slats of certain sieve sections can be sized proportionately relative to other sieve sections. This allows a broader distribution of the crop layer or mat along the length of the sieve to promote the passage of air therethrough thereby promoting the cleaning efficiency of the cleaning section of the combine.
To adjust the different sieve sections a series of levers or handles together with a series of connecting linkages are normally provided in association with each sieve. More specifically, an adjusting lever is connected to each sieve section as through a linkage to angularly adjust the slat rows in a particular sieve section. Certain sieve sections, mainly in the rear of the sieves, require only infrequent adjustment. Each lever or handle must be independently adjusted to effect the desired openings between adjacent slats of a particular sieve section.
The disadvantages of these prior arrangements reside mainly in that proper adjustment of the openings is difficult to attain. Also, it is almost impossible to repeatedly return the slats to precisely their originally set position following adjustment thereof. Providing a lever or handle along with connecting linkage for each sieve section increases the manufacturing costs of the sieve and of the combine. As will be appreciated, providing a lever or handle together with a connecting linkage for each sieve section furthermore increases maintenance costs and requires an additional inventory of parts to maintain the sieves in proper working order.
Because of the several drawbacks associated with rising levers to effect proper adjustment of the openings between the sieves, it is known to provide a rotatable knob to replace the adjusting lever or handle of heretofore known sieve adjustment assemblies. In such arrangements, the rotatable knob is typically arranged in threaded association with an elongated nonrotatable linkage which endwise moves in response to turning of the rotatable knob thereby resulting in adjustment of the angular relationship of the slats relative to each other. While offering improved sieve adjustment abilities, such rotatable knobs did little or nothing to reduce the number of parts required for effecting adjustment of the various cleaning section of the combine sieve.
During their operation, combines generate a great deal of dust and dirt. The reciprocating action of the sieves coupled with the blowing action of the fan causes the environment in the cleaning area of the combine to be particularly laden with particles of dirt and dust. These dirt and dust particles cause numerous problems when they find their way into certain places within the combine. One of the major problems caused by such dirt and dust particles is the freezing of parts that are normally in movable relation to one another thereby not allowing relative motion between the otherwise movable pans. This is especially true in those situations where rotatable knobs are used to adjust the openings in a particular section of the cleaning sieve. The dust and dirt particles often contaminate the threaded connection between the rotatable knob and the linkage making it difficult if not impossible to turn the knob to adjust the slats angular relationship relative to one another.
Another problem with some known cleaning systems is that grain tends to congregate toward a forward area of the sieves. The front cleaning section of the sieve is substantially closed or has a very small opening between adjacent slats of that section so that the materials will tend to move towards the rear section of the sieve thereby spreading the crop layer or mat over a greater area. It is difficult, however, for the operator to properly adjust the angular disposition of the sieves thereby adjusting the openings between adjacent slats in the front section of the sieve relative to the adjustment of the angular disposition of the slats at the adjacent lengthwise sections of the sieve.
The foregoing illustrates numerous problems and limitations of the known prior art mechanisms. Thus, it is apparent that it would be advantageous to provide a cleaning system which embodies sieves having more than one adjustable section and wherein the adjustable sieve sections are controlled by one mechanism. It would also be advantageous to provide a sieve adjustment mechanism including a rotatable controller that is threadably connected to an elongated slat adjustment member wherein the threaded connection between the adjustment member and the controller is protected frown being contaminated with dust and dirt particles natural to the combine environment.